A Silicon Valley drugmaker focused on anti-aging treatments has raised $116 million from investors to support the development of medicines designed to help people stay healthy as they grow older.

Unity Biotechnology said Thursday that it attracted support for the Series B funding round from traditional biotech investors including Fidelity Management & Research, Arch Venture Partners, Partner Funds Management and Venrock. The San Francisco-based startup is also backed by Bezos Expeditions, the investment arm of Amazon.com Chief Executive Officer Jeff Bezos.

At first glance, Unity's vision seems like a fantasy.

"A win state for us would be if, 25 years from now, people coming of age grow up in a world where it's considered relatively normal to have an extended average lifespan, and more profoundly, it’s an era where osteoarthritis and age-related eye diseases are only things you read about in books," President Ned David said in a phone interview.

While ambitious, David says the biotech startup is grounded in serious science. Unity focuses on so-called senescent cells in the body that have stopped dividing. Studies have shown that senescent cells are associated with chronic inflammation and accumulate in the same areas where age-related diseases appear, such as aching joints, degenerating eyes and diseased hearts, David said.

Startup experienceThe company also points to its experienced management. David and Chief Executive Officer Keith Leonard previously co-founded Kythera Biopharmaceuticals, a maker of treatments for double chins and male pattern baldness. They sold the company to Allergan Plc for $2.1 billion in June 2015. David is also a partner at Arch Venture Partners, which invested in this round.

Unity is part of a wave of new companies chasing after the fountain of youth. Calico, a subsidiary of Google parent Alphabet Inc. founded in 2013, has partnered with biotechnology firm AbbVie, though it has been secretive about what it's working on. Elysium Health is another startup that's already selling a dietary supplement that it claims will help with metabolic processes such as cellular detoxification and DNA repair.

Despite the avid interest, anti-aging has been hard to crack. Pharma giant GlaxoSmithKline Plc made a $720 million bet to acquire Sirtris Pharmaceuticals in 2008, a biotech that aimed to use a compound found in red wine and said to have life-extending powers. Glaxo then shelved the leading drug candidate in 2010 after kidney damage developed in some patients.

Unity is the 10th biotechnology startup to complete a fundraising round for $100 million or more in 2016, according to research company PitchBook Data. The largest deal was Moderna Therapeutics’ $474 million Series F round in September, according to PitchBook.

Fat-Mice studyTwo of Unity's co-founders, who work at the Mayo Clinic and the Buck Institute for Research on Aging, published results on Thursday from a mouse study in the journal Science. The study shows that senescent cells are key drivers of plaque formation in atherosclerosis, a disease in which plaque buildup narrows the arteries, potentially causing heart attacks or strokes. Clearing those cells in mice fed a high-fat diet reduced the plaque and also made it less likely to break into pieces that can block blood vessels.

While that's great for the mice, rodents historically have not been reliable proxies for human outcomes.

Unity plans to start human trials in the next 12 to 18 months, beginning with eye diseases, including glaucoma and age-related macular degeneration, and osteoarthritis, according to Leonard. The company's drug will be injected locally into the eye or joint to wipe out the senescent cells.

Clear pathwaysThe company is starting with well-known diseases with clear pathways for how to get the drug approved by regulators, Leonard said. In the future, though, Unity would consider testing drugs that more broadly help to increase a patient’s “healthspan,” meaning how long they continue to stay healthy even as they age, he said.

Ultimately, patients shouldn’t expect to be able to live a whole lot longer, David cautions. While studies have been able to improve the average lifespan of mice, there’s little effect on the maximum number of years, he said.

"We don't expect people to be living to 150 years, even in the wildest version of success," he said. "But we do expect people to live free of a variety of chronic diseases."